The present disclosure relates to a wakefulness determination method, and particularly to a wakefulness determination method that can accurately determine wakefulness of a person.
Recently, for stably driving a vehicle, it has been necessary to detect a change in a physical condition of a driver. Therefore, various techniques are provided in which various parameters indicating conditions of the driver are detected and calculated to thereby determine a change in a physical condition, in particular, wakefulness of the driver.
For example, Patent Document 1 describes the technique where a pressure signal is detected with a pressure sensor on the basis of a load applied from a person and a respiration interval (RI) and a Respiration root Mean Square Successive Difference (RrMSSD), which are associated with respiratory data of a person, are calculated based on the detected pressure signal to thereby perform wakefulness determination in accordance with changes in values of the RI and the RrMSSD. Specifically, a wakefulness-maintenance apparatus according to Patent Document 1 is configured to determine that drowsiness occurs when an increase of RI and an increase of a predetermine amount of RrMSSD have simultaneously occurred (to determine that the person is in a state of low wakefulness).
According to the technique of Patent Document 1, the wakefulness determination is performed by taking, in particular, RrMSSD as an indicator and thereby momentary variations in RI can be accurately obtained. Therefore, the wakefulness determination can be performed while the influence of vibration noises due to external factors, for example, a situation where a person drives a vehicle, is reduced.
PATENT DOCUMENT 1: JP2015-80521A
However, when a person is in concentration of attention where the person temporarily holds his/her breath or when a person is having a conversation, RI and RrMSSD may simultaneously increase. Therefore, even when the person does not really feel drowsy, the occurrence of drowsiness may be wrongly determined. Also, the relationship between changes in RI and RrMSSD values and a condition where drowsiness occurs depends on characteristics of individuals. Therefore, it is difficult to accurately determine wakefulness. Thus, a technique by which wakefulness of a person can be more accurately determined has been desired.